The invention relates to a system and method for narrow channel spaced dense wavelength division multiplexing, and more particularly relates to a narrow channel spaced dense wavelength division multiplexing system and method using circulators, fiber Bragg gratings, and staggered optical filters to operate with greater efficiency.
Conventional optical communications systems employ optical fibers as transmission mediums. Each optical fiber can carry more than one optical signal at a time. In order to maximize the amount of information that is sent over such optical fibers, conventional optical communications systems typically transmit multiple optical signals concurrently over a single optical fiber. Each optical signal is a modulated signal at a particular wavelength. As will be described below, conventional optical communications systems use multiplexing and demultiplexing to transmit the multiple optical signals.
Typical optical communications first multiplex a collection of separate signal channels (e.g., wavelengths) into a single transmission medium (e.g., optical fiber). The medium then carries the multiplexed signal channels from an origination point to a destination point. The systems then demultiplex, or separate each of the signal channels back into their original state, at the destination point of the transmission medium.
Conventional optical communications systems often employ add and drop capabilities. Individual channels may be added or dropped from the multiplexed transmission medium at any point between the origination of the signal channels and the destination point. Channel add/drop must be able to add individual signal channels and remove individual signal channels as desired.
The technology of wavelength division multiplexing experiences some level of through traffic signal loss. One additional desire in multiplexing technology is to multiplex/demultiplex, and add/drop channels in the most efficient manner possible, so as to reduce the level of through traffic signal loss as much as possible.
There exists in the art a need for a system and method to perform narrow channel spaced dense wavelength division multiplexing (xe2x80x9cDWDMxe2x80x9d) in a more efficient manner. The present invention provides an efficient mechanism for DWDM that is especially useful at add/drop nodes of an optical communications network. An optical multiplexor/demultiplexor with channel add/drop, in accordance with one aspect of the present invention, includes a first circulator and a second circulator. A first fiber Bragg grating couples with the first circulator and the second circulator. A second fiber Bragg grating couples with the second circulator. The fiber Bragg gratings separate optical signals in an interleaved manner.
The optical multiplexor/demultiplexor with channel add/drop, according to another aspect of the present invention, further includes at least one optical filter in communication with the first circulator. The system can further include at least one optical filter in communication with the second circulator as well. The optical filters are spaced apart a greater distance with respect to channel spacing than the channels passing through the system. However, the unique combination of the circulators and fiber Bragg gratings allow the filters to function at the wider spacing to add/drop channel signals.
The system, according to further aspects of the present invention, has 50 GHz fiber Bragg gratings, in combination with 100 GHz optical filters, as one embodiment. The arrangement of the fiber Bragg gratings and the circulators enables the use of the 100 GHz optical filters for more narrowly spaced signal channels.